Daily rhythm of nacl intake in rats fed low-calcium diet: relation
to plasma and urinary minerals and hormones.
Tordoff, Michael G., and Atsushi Okiyama.
Monell Chemical Senses Center, 3500 Market St., Philadelphia, PA
19104, USA and Food Research and Development Laboratories, Ajinomoto
Co., Inc., Kawasaki, Kanagawa 210, Japan
APStracts 2:0278R, 1995.
To assess daily rhythms of salt appetite, we measured spontaneous 300
mM NaCl intake of male Sprague Dawley rats fed diet containing 150 or
25 mmol Ca2+/kg. Both groups drank most NaCl at night but as the dark
period progressed, intakes of controls remained constant or
diminished whereas intakes of rats fed low-calcium diet increased.
During the late dark period, when the difference in NaCl intake
between the two dietary groups was greatest, rats fed low-calcium
diet lost more corticosterone and sodium in urine, had lower plasma
osmolarity, and had higher plasma ACTH and corticosterone
concentrations than did controls. Over the 24-h cycle, rats fed the
low-calcium diet excreted less calcium and more corticosterone in
urine than did controls. They also had consistently lower plasma
concentrations of calcium and renin activity, and consistently higher
plasma phosphorus, AVP, PTH, T4, calcitonin, and 1,25(OH)2D. These
findings support the hypothesis that salt appetite induced by dietary
calcium deficiency involves a subtle dysfunction of the ACTH
-corticosterone axis, but they also raise several other possibilities.
Received 13 June 1995; accepted in final form 2 October 1995.
APS Manuscript Number R357-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 November 95